Transactivation is a technique used in molecular biology to control gene expression by stimulating transcription. During transactivation, the transactivator gene and special promoter regions of DNA are inserted into the genome at areas of interest. The transactivator gene expresses a transcription factor that binds to specific promoter region of DNA. By binding to the promoter region of a gene, the transcription factor causes that gene to be expressed. The expression of one transactivator gene can activate multiple genes, as long as they have the specific promoter region attached. Because the expression of the transactivator gene can be controlled, transactivation can be used to turn genes on and off. Also, if this specific promoter region is also attached to a reporter gene we can see when the transactivator is being expressed.